It has long been recognized that the physical properties that make certain polymers desirable for particular applications are unsuitable for other applications requiring specifically different physical properties. This has led to attempts to prepare polymeric materials possessing characteristics that would make them suitable in specific applications for which satisfactory polymers have hitherto been unavailable. One approach to achieve such products involves the preparation of "customized" polymers whose physical properties match the properties needed in the applications for which the polymers are required. Such preparations are not always technically possible, however, and even in those instances where suitable new polymers are discovered, it is often found that their necessary raw materials, or their process of synthesis, or both, involve manufacturing costs of such magnitude as to make the production of the polymers impractical from a commercial point of view.
A different approach commonly resorted to has been to identify the physical properties required of polymers suitable for the applications identified, and then to prepare physical blends of different polymers, each having individual characteristics that respond to a particular need required of the products, the aggregate of the characteristics defining the physical properties necessary for the application.
While the latter approach has met with much success, there have also been drawbacks to the preparation of polymeric blends whose individual components exhibit one or more of the properties sought for a particular application.
One problem, for example, has been the inability of the mixed polymer blends to establish the degree of physical integration of the polymers necessary to assure that each is able to contribute the different physical properties unique to itself, the combination of which is needed to meet the requirements of a particular application, requiring a specific group of physical characteristics.
An example of a somewhat different blend approach is to be found in the work of Allen and his co-workers, Polymer, Vol. 14; 597, 604 (1973); Vol. 15; 13, 19, 28 (1974).
In that work, polyols were reacted with diisocyanates and vinyl monomer, in the presence of a urethane catalyst, to give polyurethane polymers containing the vinyl monomer. Thereafter, the addition of a standard, non-reactive, azo initiator resulted in the polymerization of the vinyl monomer, giving a two-phase, blended system. While these products were reported to exhibit impact resistance in the order of that shown by high-impact polystyrene, or acrylonitrile-butadiene-styrene terpolymers, polymer blends thus formed lack the points of interconnection between the phases that have been found necessary to produce the enhanced interphase adhesion, and superior physical properties of the interconnected blended polymers disclosed herein.